This invention relates to a commutator motor, and more particularly to a radio noise preventing device for use in a commutator motor.
Heretofore, in order to reduce a radio noise generated during a driving operation of a commutator motor, a radio noise preventing device as shown in FIGS. 1 and 2 has been proposed. In FIGS. 1 and 2, a common ground terminal 2 of radio noise preventing capacitors 1 is connected to a stator core 3, to form closed loops 5 and 5', whereby an unsymmetrical noise component contained in a power source is fed-back to an armature 4 to attenuate the noise component. Reference numerals 6 and 6' designate field windings.
In this case, however, an impedance value of a capacitor defined by an air gap between the armature and the stator core is considerably high to low frequency noise, and therefore a sufficient radio noise suppressing circuit effect may not be attained.